shared folder on briefcase with 2 account on the same pc

I create a folder on user1's briefcase, i share it with user2; user2 receive mail by user1 and accept shared folder, i click on folder shared of user1 to open it to upload a file and...voila'..the folder does not exist.

I know that this is an extreme case, as the 2 account are opened on the same pc, and there is no sense to have a shared folder, but maybe that it is a bug, nevertheless.